Can a chosen definition be "wrong"?
No. If you choose a definition, then you can define a sound or series of characters to mean whatever you want them to mean. For instance, if you wanted you could declare that whenever you say "phloop" you mean one of those little paper umbrellas that are sometimes found in Piña coladas. That would be weird, but it wouldn't be "wrong."
But we suggest that there are at least 7 ways a definition can be "lousy." By understanding what makes a good definition and what makes a lousy one, you can better formulate your ideas, and you can better spot mistakes in other people's arguments. For instance, you might be in a situation where you’re trying to define the essence of an idea you came up with, or characterize the unique career role that you’ve designed for yourself. Alternatively, you might be struggling to understand a definition that someone else is using and you want to diagnose why exactly you’re finding it confusing.
The words we use are crucial to the success of the interactions we have, and it is very handy to be able to pinpoint when a particular word is making a conversation more confusing than it needs to be. So, here are the things that we think make for lousy definitions!
1. Miscommunication
If you decide the word “dog” refers to cats, people are going to be very confused.
Similarly, if you're talking to someone who uses the word "racism" to mean X (say, "an explicitly held and endorsed belief that some racial groups are inferior to others"), and you use it to mean Y (say, "any form of negative generalization or attitude to a racial group, whether it's implicit or explicit"), your conversation is probably not going to go as well as you would like until you identify that difference in usage. For these reasons, good definitions shouldn’t reuse terms that people are already familiar with or have multiple meanings associated with them. A good way to avoid the latter is to clarify upfront what you mean when you’re using a particular definition if the other person might not know what you mean with the word.
2. Irrelevance
If you define a “dooooog” to be a dog with more than 5 legs, you’re not going to find it to be useful for much of anything. Dogs like that probably do exist, but are not something almost anyone ever needs to refer to. We want our definitions to aim towards the things we are likely to want to reference.
For instance, someone bothered to define the word "Rasceta" to mean the crease commonly found going across a person's wrist. Presumably there is some subculture where that is a useful word, but very few people will ever need to know that definition.
3. Unnaturalness
If you define “dogephant” to include all dogs smaller than 10 pounds AND all elephants more than 8000 pounds, you have not “carved reality at the joints.” Because of mixing things that aren’t clearly alike, using this definition makes communicating more muddled than it needs to be.
Another instance of this phenomenon is our use of the word “selfish.” Sometimes people define the word "selfish" in such a way that it includes both "stealing money from someone" and "sacrificing your own life to save the life of ten others because you feel such a strong emotion of compassion for those people;" it’s about doing things that make you feel "good." An alternate reading of selfish might be much more negative; it’s about taking actions which benefit you at the cost of other peoples’ wellbeing.
4. Opinionatedness
If you define “dogmor” to be “those dog loving morons who somehow are convinced that dogs are better than cats,” then the definition imports both a debatable opinion and an emotional slant into its meaning, causing usage of this word to be infected with either or both of these things.
For example, the word "sissy" not only suggests that someone -- usually a boy or man -- embodies feminine qualities, but carries with it a negative, insulting connotation. If your aim is to make certain people feel bad, then this might be a good strategy to take, though you might be being a jerk, and that approach doesn’t make for clear, unbiased communication.
5. Ambiguity
If by “dogdog” you mean anything that a dog can like, then your word is (1) hard to use and (2) hard to think about; dogs like a large range of things and individual dogs also have distinct preferences!
The word "problematic" (when used without clarification) is another (problematic) example of a definition: the problem being referred to could be of many different types, and could range from quite objective to just the idiosyncratic, subjective opinion of the writer.
6. Inefficiency
If you define "doglegs" to be anything with the legs of a dog, and "dogface" to be anything with the face of a dog, etc., then you can talk about walking your dog by saying "I just got back from walking a creature with doglegs, dogface, dogfur, dogheart, ..." But this is a ridiculously inefficient way to talk about your dog! Some definitions make communication substantially more efficient since they compress lots of information you commonly want to express into a small package.
Consider a different instance of this: it is possible to talk about calculus without having a word that means “the derivative” (e.g., by always referring to "limits of functions") but this is going to be a painful and inefficient way to think and communicate. The word derivative makes ideas in calculus much easier to talk about.
7. Precision
If you define "floofster" to be any animal with fur, then you will not be communicating very precisely when you say "I pet my floofster this morning." You may be saying something true (and rather adorable), but someone will not know if you were petting a dog, a cat, or something more exotic like a lizard wearing a fur coat! Ideally, we want our definitions to focus on just those items or concepts we are trying to communicate.
Similarly, if you say to your friend "I'm feeling bad," the ambiguity of the word “bad” makes it harder for them to understand what you're going through. If you say "I have a headache" then it will be easier for your friend to help you. Even better, if true, would be to say "I have a migraine."
So, no chosen definition can be “wrong,” but plenty are “lousy.”
To prevent lousy definitions, you should choose definitions that (1) allow clear communication, (2) refer specifically to the things of interest, (3) carve reality at the joints, (4) don’t sneak in debatable opinions/slants, (5) are relatively unambiguous, (6) express more information in fewer words, and (7) be more exact and specific with our words. We hope you found this helpful!